Children born premature are at risk for problems in physical, cognitive and affective development. One potential biochemical precursor of dysfunction is (blood) bilirubin. Bilirubin, which causes jaundice, is neurotoxic: At high levels (greater than 20 mg. %) it causes mental retardation. Bilirubin levels in preterm infants are often elevated. It is hypothesized that a significant portion of the diverse, adverse sequelae of preterm births may result from the presence of this neurotoxin, bilirubin, which damages many regions of the brain shortly after birth. The purpose of this research is to determine if the amount of impairment in early affect expression (cries), neurological performance and visual function in preterm infants is associated with concentration of bilirubin in the blood.